The technical field of this invention is the removal of hair and inhibition of hair regrowth by devitalization of certain hair structures within hair follicles.
Individual hair follicles comprise a bulb or cavity below the surface of the skin, from which a body of soft keratin is extruded. This shaft of keratin hardens as it passes through the bulb and ultimately protrudes from the skin surface as a "hair." A small cellular structure at the bottom of the cavity, the papilla, together with ancillary germinative structures, is responsible for the extrusion of the keratin which eventually forms into a hair. Permanent hair removal requires devitalization of the papilla or the structures that surround it.
The removal of body hair, a process commonly known as depilation, has been practiced with varying degrees of success for centuries by diverse methods and devices. For example, hot wax can be applied to a skin surface and allowed to harden around body hairs. Once the wax has hardened, it can be removed as a sheet, taking with it those hairs that have been entrapped by the wax. Typically, this is not a permanent process because the removal of the hair shaft does not prevent the regrowth of new hair from the shaft.
Various chemical depilatories have been used to remove hair. Typically these chemical agents are caustic, e.g., sodium hydroxide and the like, which makes the treatment process painful. Moreover, chemical depilatories are often not very effective.
Another approach to depilation is the use of electrical currents to destroy the delicate structures of the hair root. For example, U.S. Pat. No. 5,049,148 issued to Mehl discloses an electrical device of this nature. Similar devices, generally known as "electrolysis" devices have been used in various forms, with and without the assistance of chemical adjuvants. However, electrolysis is time consuming because the electrical current must be applied to each hair follicle individually.
An alternative approach for permanently impairing regrowth of many hair follicles at once is disclosed in U.S. Pat. No. 5,470,332 issued to Mehl et al. which involves the application of a conductive material to the skin's surface and then applying an electric current to this conductive layer.
Most recently, a number of techniques for photocoagulation of the delicate hair structures by laser irradiation have been disclosed. For example, U.S. Pat. No. 5,595,568 issued to Anderson et al., U.S. Pat. No. 4,388,924 issued to Weissman, et al., and U.S. Pat. No. 5,059,192 issued to Zaias disclose such laser irradiation techniques.
In addition, U.S. Pat. No. 5,425,728 and U.S. Pat. No. 5,226,907 issued to Tankovich disclose laser techniques in which the hair follicles on a section of skin are first contaminated with a substance (i.e. carbon particles) that has high absorption of light within a specific frequency band. The skin is then illuminated with such light, typically from a laser source, to heat the contaminating substance and kill the follicles or skin tissue feeding the hair root.
None of the processes described above are totally effective in depilating skin. There exists a need for better and more effective techniques. Accordingly, better methods and devices for hair removal would satisfy a long-felt need in the art.